The invention relates to a device for the force transmission in brake boosters where the control force and the boosting force are added up and transmitted to the hydraulic system actuation device by means of radially arranged levers.
In particular, in the case of vacuum boosters, it is known to provide radially arranged levers for the transmission of the control force, on the one hand, and of the pneumatic boosting force, on the other hand, to the actuation device.
In the German Pat. DOS No. 1,430,633 a vacuum booster is described which has a cup-shaped cylinder, a cover fixed thereon, and a piston displaceable therein. Via three radially disposed levers in piston rests on a disc with an actuation rod for an oil pressure cylinder and on a sleeve which is slipped on to a control rod projecting through the central opening of the piston. The radially disposed levers are designed as two-arm levers, at the inner ends of these levers which face one another the control force generated by the driver being applied via the control rod and the slipped-on sleeve and at the outer ends of these levers the boosting force is applied which acts on the piston which is displaceable in the cup-shaped cylinder. The balancing point of the levers lies on an imaginary circle of the disc connected with an actuation rod of the oil pressure cylinder. The vectors of the control force and of the boosting force at first are summed up at any of the individual levers to form a force vector which in the balancing point of the lever is vertically directed to the above-mentioned disc. Since the imaginary circle on this disc on which the balancing points of all the levers provided are situated lies concentrically in respect of the actuation rod of the oil pressure cylinder and since the forces becoming effective at the various levers are equal components of the control force and the boosting force the total vector of the forces transmitted to the actuation rod exactly lies on the imaginary axis of the imaginary circle.
This arrangement of the levers at the same time forms the reaction element which substitutes the reaction disc or reaction diaphragm, respectively, of other designs and which by means of the ensuing reaction force which is transmitted to the control element actuated by the driver correspondingly gives the driver a feeling for the total braking force actually generated.
The disadvantage of this arrangement and of similar ones is that the insertion of the individual levers means a complicated and time-consuming assembling operation. With regards to boosters with different transmission ratios, correspondingly, there exist differently designed levers as the balancing points and the lever arms of the levers must change if the transmission ratio is to be varied. Therefore, upon insertion of the individual levers there will be often a faulty assembly because of assembling levers of the type referred to with varying transmission ratios in a booster, therefore, the operability of the booster is disturbed.
The British Pat. No. 979,418 describes a vacuum booster where for the purpose of functionally distributing the forces which become effective in different ways there is also provided levers in a radial arrangement which is concentric to the control and actuation devices. Here, the control force and the boosting force which become effective on a wall-shaped piston provided in the housing by means of pressure differences are also transmitted to the actual actuation system of the hydraulic system by means of radially disposed levers. A transmission elemeent of the control piston will abut the radially inner free ends of the levers upon the actuation of the system. The radially outer ends of the levers are interconnected as well as connected with a ring element by means of a rubber ring vulcanized to the outer ends of the levers. Via this rubber ring the levers abut a hub element connected with the wall-shaped piston so that the boosting force will apply to just these outer ends. A reaction ring of elastic material is provided on the hub element at a certain radial distance from the outer ends of the levers, the flat-shaped levers resting on said reaction ring. An annular transmission element receives the control and boosting forces at the opposite ends of the levers and transmits these forces summed to the actuation device of the hydraulic system.
As regards the assembly, here, the levers to be inserted are connected with one another by means of the rubber ring vulcanized to their outer ends. However, handling the levers when inserting them will be rather complicated. Admittedly, the danger of faulty assembly will be reduced by a certain amount, but because of the interconnection of the levers at their outer ends, the inner ends remaining entirely free. Thus, a structural element will result which in its entirely will be extremely flexible and unstable and which for the insertion requires even more handiness than the levers which are to be inseted separately.
The connection of the levers at their radially outer ends by means of a rubber ring vulcanized to them, however, was not meant to be a help in the assembly by the inventor of the above-described system.